shared memory segment can't be removed after call shmdt() - c++

Question

i called shmdt() successfully, but shared memory segment can't be removed..
this is my code:
#include <sys/types.h>
#include <sys/shm.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
int main() {
key_t key = ftok(".", 'T');
if (key == -1) {
fprintf(stderr, "get key failed, error: %s\n", strerror(errno));
exit(1);
}
int shmid = shmget(key, sizeof(int) * 10, IPC_CREAT);
if (shmid == -1) {
fprintf(stderr, "get shmid failed, error: %s\n", strerror(errno));
exit(1);
}
void* shmaddr = shmat(shmid, NULL, 0);
if (shmaddr == (void*)-1) {
fprintf(stderr, "get shmaddr failed, error: %s\n", strerror(errno));
exit(1);
}
if (shmdt(shmaddr) == -1) {
fprintf(stderr, "detach failed, error: %s\n", strerror(errno));
exit(1);
}
return 0;
}
after that, i execute ipcs -m
# ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x00000000 1179648 root 0 4 0
0x00000000 1212417 root 0 4 0
0x00000000 1245186 root 0 4 0
0x00000000 1277955 root 0 4 0
0x00000000 1310724 root 0 4 0
0x00000000 1343493 root 0 4 0
0x00000000 1376262 root 0 4 0
0x00000000 1409031 root 0 4 0
0x00000000 1441800 root 0 4 0
0x00000000 1474569 root 0 4 0
0x54010004 1671178 root 0 40 0
0x00000000 1540107 root 0 4 0

Answer 1

shmdt() detaches the shared memory segment located at the address
specified by shmaddr from the address space of the calling process.
The to-be-detached segment must be currently attached with shmaddr
equal to the value returned by the attaching shmat() call.
shmdt only detaches the calling process from attached memory. It will not remove the shared memory created by the process.
For more information please read the man page of the respective system calls.